viewof prime = {
const min = 0, max = 1000, value = 100;
const primes = getPrimes(min, max);
let i = 0;
while(primes[i+1] <= value) i++;
return slider({
value: this ? this.input.value : i, step: 1, max: primes.length - 1,
getValue: n => primes[n.value]
});
}